How do I built a rabbit ears antenna?
I would like to know how a rabbit ears antenna work, like the one shown in the picture below.
I need to know how much length the two whip antennas have, and how much gap should there be between them to make them work as a dipole antenna?
Also, how is the loop length is calculated for such a single loop UHF antenna?
How are all the three antennas connected in this rabbit ears antenna?
Because the question is lacking specifics, this answer is lacking specifics.
I need to know how much length the two whip antennas have, and how much gap should there be between them to make them work as a dipole antenna?
The appropriate length is frequency dependent, so you should choose a length that is appropriate for the frequency that you are looking to receive.
The gap should be as small as practical. I have no idea of the appropriateness of the antenna to your need since you omit it. Suffice it to say that it's not critical and shouldn't be high up on a list of concerns for any practical antenna build.
How are all the three antennas connected in this rabbit ears antenna?
In my experience, the VHF and UHF antennas are connected via separate transmission lines to the TV. The VHF using coax and an F-style connector (IIRC) and the UHF using twin-lead and a balun. Or maybe the other way around. you can google to figure which is which.
The rabbit ears are 2 elements of a single VHF antenna (yes, a dipole!), one of which is connected to the shield of the coax transmission line, the other of which is connected to the center conductor.
Each end of the UHF loop is connected to one of the twin-lead wires.
I'm sorry there isn't more to share here, but that's mainly a result of the vagueness of the question.
You now have four threads open asking for the same information repeatedly. There is a lot of information on antennas on the net. The rabbit ears you keep showing are from the 50s era, and if you open them up, you will be disappointed; there is no magic inside.
There is no specific distance between the dipole terminals. On an HF dipole, the distance is up to many inches. The feed impedance sets the distance on a machined factory-made folded UHF dipole found on a stacked array or Yagi. Inside those rabbit ears, the coax splits inside, with the coax shield going to one of the telescoping VHF dipoles and one end of the UHF loop. The center conductor is connected to the other dipole and the end of the loop. Both the UHF loop and the VHF dipoles are in parallel.
The rabbit ears antenna is strictly an RX antenna made for John Public. The UHF loop is pretty much useless because the size is fixed. It works somewhat on one channel and poorly on the other 83. The telescoping dipoles can be helpful and make a decent antenna if you know what wavelength you are trying to receive and in which direction the station is. Tune the dipoles, lay them flat, and orient at a right angle to the station.
Keep this in mind: almost every antenna out there is a dipole. You have to look at it. For example, a vertical monopole is a dipole. The vertical is one leg, and the radials are the other leg. An End-fed antenna is an off-centered dipole. It takes two to tangle the RF dance. Every electrical circuit out there requires a supply and a return conductor.
